Control devices for watercrafts in the prior art are provided in different forms and operate with different principles.
Some of the control devices in the prior art are merely mechanical and include a mechanical cable transmitting the command signal. The mechanical cable is operably and dynamically coupled to the lever and transmits all information regarding the desired position of the lever and the displacement direction of the lever, i.e. the gear to be set and the opening position of the throttle, by moving the cable inside its sheath based on the displacement of the control lever. Information is transmitted to an electromechanical actuator or in certain cases directly to the control member of the motor/transmission assembly, for example directly to the throttle and/or reversing gear.
Therefore, these types of control devices operate on the basis of a mechanical transmission of motion and force.
These types of merely mechanical control devices are inexpensive but suffer from certain drawbacks. Operation, above all in middle-sized watercrafts where the mechanical cable has a considerable length, requires a considerable force on the control lever, moreover, due to assembling and operating tolerances, the command signal is inaccurately transmitted. Other drawbacks are due to the fact that in marine applications a mechanical cable is easily subjected to incrustation, causing malfunctions and/or the transmission of the command signal to be stopped. Moreover, a mechanical cable needs frequent maintenance, above all in an aggressive environment such as the marine environment, causing the user to provide an expensive maintenance. The installation of a device of this kind is also complicated and expensive.
Today, such a merely mechanical device is becoming outdated and it is typically mounted only onto very small-sized and economic watercrafts.
A second type of control device in the prior art is electromechanical. The control lever essentially generates two parallel signals, a first mechanical signal, going for example along a mechanical cable that is dynamically connected to the control lever of a control station, such as the completely mechanical device described above, and a parallel second electric signal, generated for example by a potentiometer connected to the control lever or to another type of electromechanical transducer. The electric signal correspondingly drives an electromechanical actuator, which acts on a member of the motor assembly, for example the throttle, and reduces the force the user needs for acting on the lever, causing a known electromechanical interlocking.
This electromechanical control device exhibits some drawbacks. The signal is not optimally and precisely transmitted, since a part of the signal is transmitted by a mechanical cable, having the drawbacks listed above, in a manner that is similar to the merely mechanical embodiment.
Due to these drawbacks, such electromechanical control devices are not recommended for middle-sized and middle-cost watercrafts, and are more preferably used on economic and small-sized watercrafts.
Another type of control device is a merely electronic, digital device. In this type of device, the lever of the control station is provided with position and/or displacement sensors, which detect information regarding the position and displacement of the control member and transform such quantities into corresponding components of a command signal that is transferred by a communication line, a so-called BUS, particularly a so-called CanBUS, to a control unit of an electromechanical actuator acting on one or more control members of the motor assembly or controlled equipment. In this type of device there is a control unit, which changes the command signal that is generated and detected by sensors connected to the control lever, such that the command signal can be transferred along a merely digital line, such as CanBUS, to the actuator, which receives the command signal and carries out the corresponding action.
Moreover, the command unit includes software for checking the command signal, in order to verify if the signal is properly transmitted along the BUS, that is, if the signal coming to the actuator is the signal transmitted by the control unit.
A first drawback of this type of device is related to cost. A control unit configured to change a series of signals deriving from one or more sensors into corresponding digital command signals to be sent by a digital BUS is relatively expensive, because the signals to be changed and checked are numerous and concern the progressive position of the lever and the gear set or to be set.
Moreover, the control unit must have a relatively high computational ability, since it must be able to verify whether the transmission of digital signals along the BUS is correct, and, therefore, must implement software or similar means for checking whether the signal is properly transferred. In some cases, it is necessary for the checking software to be loaded in a no volatile memory, which is typically integrated into the unit, thereby increasing cost, complexity and sensitivity to damages or malfunctions.
In this type of device, the communication BUS must have such a size and structure to be able to transmit a considerable amount of data, measurable for example at 64 bits/second and corresponding to information about the position of the lever, the displacement direction of the lever and/or position for setting the desired gear, error checking, and error correction. Therefore, a dedicated communication BUS is required, or alternatively digital signals must be caused to pass on the common BUS mounted on all the watercraft. In this second case, the control device uses the BUS to a considerable degree and causes the speed of data transmission to increase and/or may cause error when transmitting data, so a suitably sized BUS must be employed, which is more expensive.
In other words, the amount of information passing through a communication line, for example a BUS, causes said line to be used as a function of the amount of data transmitted and received. Data that are transmitted and received are also checked to verify whether the transmission/reception is congruent, that is whether data are missed or have been transmitted incorrectly and in an incomprehensible manner. Such check is carried out by suitably transmitting additional data or detection bits, causing the BUS to be further used. Therefore, the higher the amount of information is and the more the BUS is used, the higher is the amount of data to be checked, causing the BUS to be used still more. Due to the foregoing, at least 64 bits/second are typically necessary for transmitting data regarding information about position of the lever, displacement direction or position for setting the desired gear, error check, and error correction.
A BUS, especially of the Can type, mounted on a watercraft generally is not used only by the control station, but it is also used by other watercraft equipment, such as the wheel or rudder, maneuvering propellers, watercraft lights or drive assisting systems.
The amount of information using a BUS on a watercraft, for example command signals and signals checking or verifying errors in the transmission, is therefore quite high, and the more information or data passing inside the BUS is reduced, the less the BUS is used and the transmission becomes faster and free from errors. This requires alternatively the use of a communication BUS able to stand a large amount of data, which is expensive, or the use of various communication BUSes, and, in an undesirable scenario, a BUS dedicated for each piece of equipment, with considerable drawbacks as far as costs and mounting problems are concerned.
As it can be seen, even if the merely electronic device of prior art can overcome drawbacks of the merely mechanical or electromechanical devices, a merely electronic device, in which data are transmitted only as digital signals, has a mounting cost that is considerably higher than for the other two above described types of control devices, and is suitable for the use only in large-sized and correspondingly expensive watercrafts. The cost of such a merely electronic device for middle-sized watercrafts it is often too high in relation to the cost of the watercraft itself.
With regard to reliability and to the consequences of an error in transmitting the command signal, the heavy damages should be considered that would occur, for example, during mooring if the transmission of the command signal has errors or deviations with respect to what had been set and desired by the user acting on the control lever, and the dangerous condition should also be considered that could derive from a systematic error of the control system.
Therefore, there is a need of a device, which, while acting without mechanical transmission, that is, with the transmission of electrical signals, has a limited cost, comparable or almost comparable to the cost of a mechanical or electromechanical device, and which also has a high reliability and a reduced maintenance cost, making such device comparable or almost comparable to a merely electronic device.